Blender 2.9. Flip Region missing?
To use this with Blender 2.90 or later, it seems that you have to manually add the keymap of the following command.
Settings&gt; Keymap&gt; Screen&gt;
screen.region_flip

As for the name of B's ​​menu, it looks like &quot;Redo Last&quot;.
The operator name that calls this menu in a popup is &quot;Redo Last&quot;.
screen.redo_last
Apparently it was intentionally deleted.
↓ It's not the task of this problem itself, but it says so.
⚓ T71810 UI: Flipping a Sidebar with more tabs isn't aligned correct